JP4818879B2 - Method for producing cold-rolled steel sheet with excellent ductility and room temperature aging resistance - Google Patents

Description

  The present invention relates to a method for producing a cold-rolled steel sheet having high ductility and excellent room temperature aging resistance, particularly suitable for materials for automobiles and household electrical products, building materials, and the like. In addition, the present invention includes a manufacturing method in which the surface of the cold-rolled steel sheet is further subjected to surface treatment such as Zn plating or alloyed Zn plating for rust prevention.

  Conventionally, cold-rolled steel sheets that have been softened and improved in formability by control of addition amounts of C and N, steelmaking, hot rolling, optimization in annealing processes, addition of carbonitride-forming elements such as Ti and Nb, etc. When solid solution C and solid solution N remain, strain aging proceeds at room temperature and yield elongation occurs. As a result, the cold-rolled steel sheet has a problem that a wrinkle pattern called a stretcher strain is generated at the time of pressing and the surface quality is impaired.

  Therefore, in order to ensure normal temperature aging resistance, the component composition and the manufacturing process up to annealing are optimized to reduce the amount of solid solution C and N, and furthermore, a movable transition is introduced into the bulk by temper rolling. Yes. Further, in order to promote the introduction of movable dislocations in the cold-rolled steel sheet, it is necessary to increase the elongation by temper rolling, thereby improving the normal temperature aging resistance.

  However, when the elongation rate of temper rolling is increased, the ductility of the cold-rolled steel sheet deteriorates and the formability of the product may be impaired. On the other hand, when temper rolling at a low elongation rate is performed using a conventional rolling mill in order to avoid a decrease in formability, the shape of the cold-rolled steel sheet may be impaired, for example, the flatness is lowered. Moreover, when the elongation rate of temper rolling is lowered, the elongation rate becomes non-uniform in the sheet width direction of the cold-rolled steel sheet, and sufficient room temperature aging resistance cannot be obtained at sites where the elongation rate is insufficient.

  For this reason, conventionally, the elongation rate of temper rolling has been increased so that sufficient elongation can be ensured even in a region where the local elongation is lowest in the width direction of the cold-rolled steel sheet. This has caused a slight decrease in the formability of the steel sheet.

Until now, as a method for improving the uniformity of the rolling reduction in the sheet width direction, for example, a method using a light rolling mill provided with a divided backup roll has been proposed (for example, see Patent Document 1). However, the rolling mill described in Patent Document 1 relates to a method of manufacturing a thick steel plate having a thickness of 5 mm or more, and there is no description regarding materials such as normal temperature aging resistance and ductility.
JP 2002-66603 A

  The present invention has been proposed in view of such conventional circumstances, and is excellent in ductility and room temperature aging resistance, which can ensure the homogeneity of the material in the plate width direction without impairing the shape. An object of the present invention is to provide a method for producing a cold-rolled steel sheet.

  Conventionally, in order to have sufficient room temperature aging resistance in the full width of the steel sheet, the elongation rate of temper rolling is required to be 0.8% or more, assuming a decrease in the local elongation rate, Therefore, it has been difficult to avoid deterioration of moldability. Therefore, the present invention performs temper rolling of a soft cold-rolled steel sheet in which the amount of solute C and solute N is limited by a rolling mill that supports a work roll with a divided backup roll, with a reduced elongation rate. Thus, it is possible to produce a cold-rolled steel sheet having excellent ductility and room temperature aging resistance without impairing the homogeneity of the shape and the material in the sheet width direction, and the gist thereof is as follows.

(1) One or both of the upper and lower roll assemblies have a support mechanism that supports a work roll by a divided backup roll divided into three or more in the axial direction, and a load applied to each of the divided backup rolls. A rolling mill provided with a load detection device to detect and a reduction device that raises and lowers the divided backup roll independently, the total of one or both of the solid solution C amount and the solid solution N amount is less than 0.0010%, thickness 0.3 to 2.0 mm, for the cold-rolled steel sheet strip width is 600～2000Mm, like elongation in the plate width direction becomes uniform, required to obtain a given elongation After calculating the rolling load, the rolling load for each part in the sheet width direction is detected, and the temper rolling with an elongation of 0.1 or more and less than 0.8% is performed while controlling the rolling load for each part. Features A method for producing cold-rolled steel sheets with excellent ductility and room temperature aging resistance.

(2) The component composition of the cold rolled steel sheet is mass%,
C: less than 0.0010%,
Si: 1.00% or less,
Mn: 3.00% or less,
P: 0.100% or less,
S: 0.100% or less,
Al: 1.000% or less,
N: containing less than 0.0010%, the balance consisting of Fe and inevitable impurities,
The total content of C and N is less than 0.0010%, The method for producing a cold-rolled steel plate having excellent ductility and room temperature aging resistance as described in (1) above.

(3) The component composition of the cold-rolled steel sheet is mass%,
C: 0.0500% or less,
Si: 1.00% or less,
Mn: 3.00% or less,
P: 0.100% or less,
S: 0.100% or less,
Al: 1.000% or less,
N: 0.0500% or less, the balance is made of Fe and inevitable impurities,
Furthermore, in mass%,
Nb: 0.001 to 0.150%,
Ti: 0.001 to 0.150%
One or both of
The content of C, N, Ti and Nb is
1 / 4Ti + 1 / 8Nb ≧ C + N−0.0010
The manufacturing method of the cold-rolled steel plate excellent in ductility and normal temperature aging resistance as described in said (1) characterized by satisfy | filling the relationship of these.

(4) The surface roughness Ra of the work roll is 0.2 μm or more, and cold rolling excellent in ductility and normal temperature aging resistance according to any one of (1) to (3) above Steel plate manufacturing method.

(5) Cold rolling excellent in ductility and normal temperature aging resistance according to any one of (1) to (4), wherein the surface of the cold rolled steel sheet before temper rolling is plated. Steel plate manufacturing method.

  As described above, according to the present invention, a soft cold-rolled steel sheet excellent in ductility and room temperature aging resistance is produced, which suppresses local surface quality deterioration without impairing the shape such as flatness. be able to. Further, depending on the steel type, the industrial contribution is remarkable, such as the restriction on the components and production conditions that have been the cause of the decrease in productivity can be relaxed.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
The rolling mill of the present invention has a support mechanism in which at least one of the upper and lower roll assemblies supports a work roll by a divided backup roll divided into three or more in the axial direction, and is loaded on each divided backup roll. An independent load detection device that detects the load to be detected and an independent reduction device that raises and lowers each divided backup roll individually are arranged.

  By employing this divided backup roll, the elongation in the sheet width direction becomes uniform even when temper rolling is performed at a low elongation. In the temper rolling of the present invention, since the change in the plate thickness is small, the rate of change in the length in the rolling direction, that is, the elongation rate is specified.

  When the temper rolling with low elongation rate is performed on the cold-rolled steel sheet after annealing, in which the amount of solute C and the amount of solute N are controlled by the rolling mill of the present invention, the ductility and the room temperature are not impaired without damaging the shape A cold-rolled steel sheet having excellent aging resistance can be produced.

  As shown in FIG. 1, the rolling mill of the present invention is supported by split backup rolls 3 and 4 in upper and lower inner housings that move up and down by a pass line adjuster 1 using an electric motor and a main reduction device 2 using hydraulic reduction. The upper and lower work rolls 5 are provided. The pass line adjuster 1 is a device that adjusts the pass line in response to a change in roll diameter when the roll is replaced. Further, the main reduction device 2 has a mechanism for detecting the position of the hydraulic cylinder, whereby the reduction position is measured.

  Furthermore, as shown in FIG. 2, the upper and lower work rolls 5 are supported by the divided backup rolls 3a to 3d and 4a to 4e divided in the axial direction. In addition, a load detection device that detects a load that is independently applied to each of the divided backup rolls 3a to 3d and 4a to 4e, and a reduction mechanism that moves the divided backup rolls 3a to 3d and 4a to 4e independently And a position detection mechanism for detecting the position of each divided backup roll. Although not shown, the upper and lower work rolls 5 are rotated by a drive motor to transmit torque necessary for rolling. Furthermore, a work roll chock used for replacing the work roll 5 is provided in the inner housing.

The present inventors performed temper rolling of a bake-hardening cold-rolled steel sheet using the rolling mill shown in FIGS. 1 and 2, and investigated the relationship between the elongation rate of temper rolling, ductility and age-hardening resistance.
First, C: 0.0005 to 0.0500%, Si: 1.00% or less, Mn: so that the total of the solid solution C amount and the solid solution N amount is less than 0.0010% by mass%. 3.00% or less, P: 0.100% or less, S: 0.100% or less, Al: 1.000% or less, N: 0.1000% or less, Nb: 0.001 to 0 as necessary 150%, Ti: 0.001 to 0.150% or both are contained so as to satisfy the relationship of 1 / 4Ti + 1 / 8Nb ≧ C + N−0.0010, with the balance being Fe and inevitable impurities Steel was melted and cast.

  The obtained steel slab was hot-rolled and cold-rolled to obtain a cold-rolled steel plate having a thickness of 0.8 mm. The cold-rolled steel sheet was annealed by adjusting the annealing temperature within the range of 750 to 850 ° C., the annealing time within the range of 40 to 100 seconds, and the cooling rate within the range of 60 to 120 ° C./second.

  Next, these steel sheets were subjected to temper rolling with an elongation of 0.3% by the rolling mill shown in FIGS. Further, as a comparative example, temper rolling with an elongation of 0.3% and 1.4% was performed using a normal light rolling mill composed of backup rolls that were not divided. From these cold-rolled steel plates, No. 5 test pieces of JIS Z 2201 were produced with the rolling direction as the longitudinal direction for every 100 mm of plate width. In addition, the tensile test piece was produced within one week after the temper rolling, and the tensile test piece was stored at −40 ° C. until the tensile test was performed.

  Using these tensile test pieces, a tensile test was performed in accordance with JIS Z 2241, and the yield elongation and total elongation were measured. Furthermore, the measurement of the yield elongation is performed after holding in a constant temperature room at 25 ° C. for 30, 60, 90 days, and the minimum number of days in which a remarkable yield elongation of 0.2% or more is observed is determined at room temperature aging resistance. It was used as an index. In addition, it is assumed that sufficient room temperature aging resistance is obtained when yield elongation does not appear in the test after 90 days.

FIG. 3 shows the total elongation measured by conducting a tensile test without holding at 25 ° C. after temper rolling. Moreover, the result of having evaluated normal temperature aging resistance is shown in FIG.
3 and 4, it can be seen that the steel sheet produced according to the present invention exhibits excellent normal temperature aging resistance while maintaining higher ductility than conventional temper rolling.

Hereinafter, the manufacturing method of the cold rolled steel plate excellent in ductility and room temperature aging resistance of the present invention will be described in detail.
First, the reason for limitation related to temper rolling, which is the most important process in the present invention, will be described.

(Rolling mill)
In an ordinary temper rolling mill, when temper rolling is performed with the elongation rate lowered, the elongation rate becomes non-uniform in the sheet width direction. In particular, the elongation of temper rolling becomes insufficient at the end of the steel sheet, and room temperature aging resistance cannot be ensured. Therefore, in the present invention, the temper rolling is performed by the above-described rolling mill having a mechanism capable of appropriately adjusting the elongation of the steel sheet depending on the portion in the sheet width direction.
The rolling mill of the present invention divides a backup roll in the plate width direction and controls each divided backup roll independently. That is, after calculating the rolling load necessary to obtain a predetermined elongation, the rolling load for each part in the sheet width direction is detected, and the rolling load is controlled by a separately provided reduction device. Thereby, even when the elongation rate in temper rolling is low, the elongation rate in the sheet width direction can be made uniform.

(Elongation: 0.1% or more and less than 0.8%)
Even if the rolling mill of the present invention is used, if the elongation is less than 0.1%, the purpose of shape correction cannot be achieved. For this reason, the minimum of elongation is made into 0.1% or more. Further, when the elongation is 0.8% or more, the ductility of the cold-rolled steel sheet is lowered, and the workability is lowered because the proof stress is larger than that of the original sheet, so the upper limit of the elongation is 0.8%. Less than. Preferably it is less than 0.6%, more preferably less than 0.5%.

(Work roll diameter: 30-1000 mm)
The diameter of the work roll for temper rolling is not particularly defined, but if it is less than 30 mm, it may be difficult to control the rolling, and it may be difficult to ensure a uniform rolling reduction in the longitudinal direction. Therefore, the lower limit of the diameter of the work roll is preferably 30 mm. Further, when the diameter of the work roll for temper rolling exceeds 1000 mm, for example, even if the load on both ends in the axial direction is increased, the amount of bending becomes small, and it becomes difficult to control the elongation rate by the part, so the upper limit is 1000 mm. The following is preferable. Further, in order to cause the deformation to progress uniformly in the plate thickness direction and prevent deterioration of formability due to concentration of strain on the surface layer, the diameter of the work roll is preferably more than 300 mm, and the shape with a low elongation rate In order to ensure this, the upper limit is preferably set to 800 mm or less. On the other hand, when a small-diameter work roll having a diameter of 30 to 300 mm is adopted, movable dislocations are introduced into the surface layer of the cold-rolled steel sheet, so that aging resistance is ensured.

(Work roll surface roughness Ra: 0.2 to 3.0 μm)
By increasing the surface roughness Ra of the temper rolled work roll, the coefficient of friction between the work roll and the surface of the cold-rolled steel sheet increases, and even in a region where the applied load is locally lowered, it slides. Disappears and the shape becomes good. Moreover, since introduction of movable dislocations into the surface layer of the cold-rolled steel sheet is promoted, it is preferable to perform temper rolling using a work roll having a large surface roughness Ra. In order to obtain this effect, the surface roughness Ra is preferably set to 0.2 μm or more. The upper limit of the surface roughness Ra is not particularly provided, but is preferably 3.0 μm or less from the viewpoint of practicality such as the surface quality of the cold-rolled steel sheet.

Next, the reason for limiting the chemical components will be described.
(Solution C and Solution N: Total less than 0.0010%)
In order to obtain normal temperature aging resistance, it is important to control the residual amount of solute C and solute N in the product state. When the total of one or both of the solid solution C amount and the solid solution N amount is 0.0010% or more, normal temperature aging resistance cannot be ensured even if the temper rolling of the present invention is performed. Therefore, the upper limit of the total of one or both of the solid solution C and the solid solution N is set to less than 0.0010%. Moreover, even if the elongation rate of temper rolling is lowered to improve ductility, in order to obtain excellent room temperature non-aging resistance, the total of one or both of the solid solution C amount and the solid solution N amount is reduced to 0. It is preferable that the content be less than .0008%, and when a work roll having a large diameter is used, the content is preferably 0.0005% or less.

  The amount of solute N can be determined by analyzing the filtrate according to the steel-nitride type nitrogen determination method described in the appendix of JIS A 5523. For the amount of dissolved C, the filtrate after collecting the precipitate is directly analyzed by electrolytic extraction, or the amount of C in the precipitate collected by electrolytic extraction is quantified and evaluated by the difference. It doesn't matter. Ag is preferably used as a filter for filtering insoluble residue.

(C: less than 0.0010%)
C is an element inevitably contained in the steel. When Ti and Nb are not contained, when the C content is 0.0010% or more, the amount of dissolved C increases and normal temperature aging resistance is increased. Therefore, the upper limit is preferably less than 0.0010%.

(N: less than 0.0010%)
N is an element inevitably contained in the steel, and when the N amount is 0.0010% or more, the amount of dissolved N increases and the normal temperature aging resistance decreases, so the upper limit is less than 0.0010%. It is preferable that

(Si: 1.00% or less)
(Mn: 3.00% or less)
(P: 0.100% or less)
Si, Mn, and P are elements inevitably contained in the steel and have the effect of improving the strength. However, if the content is excessive, the workability is impaired, so the upper limit is Si: 1. 00% or less, Mn: 3.00% or less, and P: 0.100% or less are preferable. In order to decrease the strength and improve the ductility, it is preferable that the upper limits of Si, Mn, and P are 0.500% or less, 1.000% or less, and 0.050% or less, respectively.

(Al: 1.000% or less)
Al is a deoxidizer and contributes to the improvement of strength. However, if it exceeds 1.000%, the workability deteriorates, so it is preferable that the upper limit is 1.000% or less. In particular, in order to improve ductility, the upper limit of Al is preferably 0.100% or less.

(S: 0.100% or less)
Since S is an impurity and deteriorates workability, it is preferably reduced. If added over 0.100%, the ductility is greatly deteriorated, so the upper limit is preferably made 0.100% or less.

(Nb: 0.001 to 0.150%)
(Ti: 0.001 to 0.150%)
Nb and Ti are elements that form carbides and nitrides. Therefore, when increasing the content of C and N, one or both of Nb and Ti may be added to control the amount of dissolved C and the amount of dissolved N. However, if the addition amount of Nb and Ti is less than 0.001%, the effect by addition is not recognized remarkably. If the addition amount exceeds 0.150%, the recrystallization temperature rises and the material deteriorates. is there. Therefore, the addition amount of Nb and Ti is preferably 0.001 to 0.150%, respectively.

  When one or both of Nb and Ti are contained, the amount of C and the amount of N can be increased. However, if the amount of C and the amount of N exceed 0.0500%, respectively, the amount of solute C and the amount of solute N may increase and the normal temperature aging resistance may deteriorate. Therefore, the upper limit of the C amount and the upper limit of the N amount are 0.0500%, respectively. In order to make C less than 0.0005%, the manufacturing cost increases, so the lower limit of C is preferably made 0.0005%. The upper limit of the N amount is preferably set to 0.0100% or less in order to ensure normal temperature aging resistance even if the elongation of temper rolling is reduced.

The relationship between Nb and Ti and C and N preferably satisfies the following relational expression (1) from the viewpoint of controlling the solute C and the solute N.
1 / 4Ti + 1 / 8Nb ≧ C + N−0.0010 (1)
Here, in the formula (1), Ti, Nb, C, and N are the contents [% by mass] of each element. When the contents of Ti and Nb are less than 0.001%, the left side is set to 0. Calculate

  Furthermore, when the content of Ti and Nb exceeds 0.100%, the amount of precipitates increases and the ductility may be impaired. Therefore, the upper limit is preferably set to 0.100%. Further, in this case, from the viewpoint of controlling the solid solution C and the solid solution N, it is preferable that the upper limit of the C amount and the upper limit of the N amount be 0.0135%, respectively.

  Moreover, you may contain 0.001-0.100% of B, Mo, Cr, V, and W which are the elements which form a carbonitride, respectively.

  The raw materials for obtaining the above components are not particularly limited, but in addition to the method of adjusting the components by iron ore as a raw material and using a blast furnace and a converter, scrap may be used as a raw material, or this may be melted in an electric furnace. . When scrap is used as all or part of the raw material, elements such as Cu, Ni, Sn, Sb, Zn, Pb may be included.

  The manufacturing method of the cold-rolled steel sheet before the temper rolling may be a conventional method, and the steel may be melted and cast, and hot-rolled, pickled, cold-rolled, and annealed to obtain a cold-rolled steel sheet. Furthermore, surface treatment such as plating may be performed. The steel slab used for hot rolling is not particularly limited, and it may be manufactured by a continuously cast slab or a thin slab caster. It is also suitable for processes such as continuous casting-direct rolling (CC-DR) in which hot rolling is performed immediately after casting.

In order to reduce the anisotropy of the steel sheet, the hot rolling finishing temperature is preferably higher than the Ar3 transformation point. Moreover, about hot rolling, you may employ | adopt the continuous hot rolling process which joins the steel piece after rough rolling, and performs finish rolling. Further, in the continuous hot rolling process, finish rolling may be performed in the ferrite region.
The winding in the hot rolling is preferably performed at 600 ° C. or higher, and more preferably 650 ° C. or higher, in order to reduce the amount of solid solution C and solid solution N due to the formation of carbides and nitrides.
The cold rolling rate is preferably 50 to 90% from the viewpoint of productivity.
The annealing temperature is preferably higher than the recrystallization temperature in order to ensure ductility, and is preferably 950 ° C. or lower from the viewpoints of restrictions due to manufacturing equipment and productivity. Moreover, in order to avoid that solid solution C and solid solution N increase by a carbide | carbonized_material and precipitate melt | dissolving at the time of annealing, it is preferable that an annealing temperature shall be 850 degrees C or less.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples, and is implemented with appropriate modifications within a scope that can meet the gist of the present invention. These are all included in the technical scope of the present invention.

Example 1
In Example 1, steel having chemical components shown in Table 1 was melted and cast, and a steel piece was hot-rolled and cold-rolled to obtain a cold-rolled steel plate having a thickness of 0.8 mm. The blanks for Nb and Ti in Table 1 mean that the analytical value was less than 0.001%. Therefore, Steel No. In (Ti / 4 + Nb / 8) − (C + N−0.001) of A to G, the numerical value of the blank element was calculated as 0. Steel No. Since H has analytical values of both Ti and Nb of less than 0.001%, (Ti / 4 + Nb / 8) − (C + N−0.001) indicates “−”.

  Steel No. 1 in Table 1 Annealing of the cold rolled steel sheets A to H is performed with the annealing temperature in the range of 750 to 850 ° C., the annealing time in the range of 40 to 100 seconds, and the cooling rate in the range of 60 to 120 ° C./second. The amount of dissolved C and the amount of dissolved N were adjusted. The amount of dissolved C was evaluated by directly analyzing the filtrate after collecting the precipitate by electrolytic extraction. The amount of solute N was determined by analyzing the filtrate according to the steel-nitride type nitrogen determination method described in the appendix of JIS A 5523.

  Steel No. 1 in Table 1 Annealing of the cold-rolled steel sheet I is an example in which the amount of solute C and the amount of solute N are larger than the range of the present invention because the steel sheet temperature is 960 ° C. and then cooled at 60 ° C./second.

  These steel sheets were subjected to temper rolling with various elongation rates using the rolling mill shown in FIGS. A work roll having a diameter of 500 mm and a cylinder length of 2070 mm is supported by a divided backup roll having a diameter of 550 mm and a cylinder length of 230 mm divided into nine in the axial direction.

  Table 2 shows the conditions and mechanical properties of temper rolling. The No. 5 test piece of JIS Z 2201 had the rolling direction as the longitudinal direction, and the sampling position in the plate width direction was the end part, the central part, and a quarter part that was in the middle. In addition, the tensile test piece was stored within −1 week after temper rolling and stored at −40 ° C. until the tensile test was performed. The yield stress, tensile stress, and total elongation in Table 2 represent the average of the test results at the end, center, and 1/4 part. For the total elongation, the end, center, and 1/4 part. The difference between the maximum value and the minimum value at the three locations was determined and indicated as ΔEL.

Moreover, the normal temperature aging resistance is the minimum in which a tensile test piece was held in a thermostatic chamber at 25 ° C. for 0, 30, 60, 90 days and a tensile test was performed, and a remarkable yield elongation of 0.2% or more was observed. The number of days was evaluated.
Furthermore, when there is a difference in elongation in the sheet width direction of the steel sheet, the shape of the steel sheet deteriorates, so the quality of the shape was evaluated visually. For example, when the elongation at the end in the plate width direction of the steel plate is large, the edge is repeatedly undulated, and when the center is large, the middle is repeatedly undulated. Moreover, the local expansion | swelling which the specific site | part of a board width direction undulates, and these may be seen combining. “◯” indicates that such deterioration of the shape cannot be visually determined, and “×” indicates that it can be determined.

As shown in Table 2, it can be seen that the cold-rolled steel sheet obtained by the production method of the present invention is excellent in room temperature aging resistance, has a high ductility, and is excellent in shape in the entire region in the sheet width direction.
On the other hand, the production No. 1 was carried out at 0.3% elongation using a conventional light rolling mill. No. 2, because the elongation rate became insufficient toward the end of the plate width, room temperature aging resistance was good at the center in the plate width direction, but decreased at the end and ¼ part, and the shape was also It is getting worse. In addition, production No. No. 3 is an example in which temper rolling with a high elongation rate is performed with a conventional rolling mill, and the variation in elongation in the sheet width direction is large. Production No. No. 10 has a large elongation at temper rolling, and therefore has a reduced ductility.
Production No. No. 6 does not perform temper rolling, and production no. Since 14 is a cold-rolled steel sheet having a large total amount of solute C and N, room temperature aging resistance is insufficient.

(Example 2)
In Example 2, the steel No. shown in Table 1 was used. About the cold-rolled steel sheets of A and D, the annealing temperature is set in the range of 750 to 850 ° C., the annealing time is set in the range of 40 to 100 seconds, and the cooling rate is set in the range of 60 to 120 ° C./second. The amount and the amount of solute N were adjusted. Thereafter, temper rolling was performed by the rolling mill of the present invention having work rolls having a diameter of 500 mm with different surface roughness Ra, and the mechanical properties at each point of the sheet width were measured in the same manner as in Example 1, and the measurement results Are shown in Table 3. Table 3 shows the production No. in Table 2 in which the surface roughness Ra of the work roll was 0.12. The results of 1 and 7 are also shown for comparison.

  As is apparent from Table 3, in the steel having the chemical component of the present invention, temper rolling is performed using a work roll having a large surface roughness Ra, and even if the elongation rate is reduced, the shape is not damaged. It is possible to ensure normal temperature aging, and a cold-rolled steel sheet having more excellent ductility can be obtained.

(Example 3)
In Example 3, the steel No. shown in Table 1 was used. The C and F cold-rolled steel sheets were subjected to continuous hot dip galvanization at a maximum temperature of 800 ° C. and immersion in a galvanizing bath followed by alloying treatment at 500 ° C. for 20 seconds. Thereafter, temper rolling was performed using the rolling mill of the present invention, and the mechanical properties at each point of the sheet width were measured in the same manner as in Example 1. The measurement results are shown in Table 4.

  As is apparent from Table 4, in the steel having the chemical components of the present invention, even in the cold-rolled steel sheet plated before the temper rolling, by performing the temper rolling under the conditions of the present invention, without damaging the shape, A cold-rolled steel sheet having excellent room temperature aging resistance and ductility is obtained.

It is a schematic diagram of the rolling mill of this invention. It is a schematic diagram of the division | segmentation backup roll of this invention. It is a figure which shows the uniformity of the total elongation of the board width direction by this invention. It is a figure which shows the uniformity of the normal temperature aging resistance of the board width direction by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Passline adjustment machine 2 Main reduction device 3, 4 Backup roll 3a-3g Division backup roll 4a-4h Division backup roll 5 Work roll

Claims (5)

One or both of the upper and lower roll assemblies have a support mechanism for supporting the work roll by a divided backup roll divided into three or more in the axial direction, and a load for detecting a load applied to each of the divided backup rolls By a rolling mill provided with a reduction device that raises and lowers the detection device and the divided backup roll independently, the total of one or both of the solid solution C amount and the solid solution N amount is less than 0.0010%, and the plate thickness is 0. .3～2.0Mm, for the cold-rolled steel sheet strip width is 600～2000Mm, like elongation in the plate width direction becomes uniform, the rolling load required to obtain a given elongation After the calculation, the rolling load for each part in the sheet width direction is detected, and temper rolling with an elongation of 0.1% or more and less than 0.8% is performed while controlling the rolling load for each part. To Excellent production method for cold rolled steel sheet in and anti-aging properties. The component composition of the cold-rolled steel sheet is mass%,
C: less than 0.0010%,
Si: 1.00% or less,
Mn: 3.00% or less,
P: 0.100% or less,
S: 0.100% or less,
Al: 1.000% or less,
N: containing less than 0.0010%, the balance consisting of Fe and inevitable impurities,
The total content of said C and N is less than 0.0010%, The manufacturing method of the cold-rolled steel plate excellent in ductility and normal temperature aging resistance of Claim 1 characterized by the above-mentioned. The component composition of the cold-rolled steel sheet is mass%,
C: 0.0500% or less,
Si: 1.00% or less,
Mn: 3.00% or less,
P: 0.100% or less,
S: 0.100% or less,
Al: 1.000% or less,
N: 0.0500% or less, the balance is made of Fe and inevitable impurities,
Furthermore, in mass%,
Nb: 0.001 to 0.150%,
Ti: 0.001 to 0.150%
One or both of
The content of C, N, Ti and Nb is
1 / 4Ti + 1 / 8Nb ≧ C + N−0.0010
The manufacturing method of the cold-rolled steel plate excellent in ductility and normal temperature aging resistance of Claim 1 characterized by satisfy | filling the relationship of these.   The method for producing a cold-rolled steel sheet excellent in ductility and room temperature aging resistance according to any one of claims 1 to 3, wherein the work roll has a surface roughness Ra of 0.2 µm or more.   The method for producing a cold-rolled steel sheet excellent in ductility and room temperature aging resistance according to any one of claims 1 to 4, wherein the surface of the cold-rolled steel sheet before the temper rolling is plated.

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